Controller of compressor

ABSTRACT

A controller of a compressor of the present invention sets a time in a timer according to a motor current detected by a motor current detector. When a time has reached the time set in the timer, the rotating speed of a DC motor is increased. Therefore, control of the rotating speed according to a load can be achieved. When it is determined that a refrigerator load is great, the compressor is operated at a higher speed quickly, while when it is determined that the refrigerator load is smaller, the compressor is operated at a lower speed, which results in energy saving.

CROSS REFERENCE TO THE RELATED APPLICATION

The disclosure of Japanese Patent Application No. 2011-200461 filed on Sep. 14, 2011, including specification, drawings and claims are incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to an inverter circuit for driving a motor by using switching elements which are PWM (pulse width modulation) controlled. Particularly, the present invention relates to a controller suitably used to drive a compressor built into a refrigerator, etc.

2. Description of the Related Art

In an exemplary conventional configuration, a controller of a compressor determines a rotating speed based on a difference between a set temperature of a refrigerator and an internal temperature of the refrigerator, and the compressor operates at the determined rotating speed (see Japanese Laid-Open Patent Application Publication No. Sho. 62-009165).

This publication discloses that the controller determines the rotating speed at which the compressor operates, based on the set temperature of the refrigerator and the internal refrigerator temperature, and causes the compressor to operate at the determined rotating speed.

Hereinafter, the controller of the compressor according to the above stated prior art will be described with reference to FIGS. 3 and 4.

FIG. 3 is a circuit diagram of the controller of the compressor according to the above stated prior art. FIG. 4 is a flowchart of a control process performed by the controller of the compressor according to the above stated prior art. Now, the operation for increasing and decreasing the rotating speed of a DC motor built into a compressor will be described.

Turning now to FIG. 3, an internal temperature detector 1 detects an internal refrigerator temperature (internal temperature of a refrigerator) and a set temperature detector 2 detects a set temperature. A controller 3 is coupled to the internal temperature detector 1 and to the set temperature detector 2, and determines the rotating speed of the operation of a compressor 8 based on a difference between the internal refrigerator temperature detected by the internal temperature detector 1 and the set temperature detected by the set temperature detector 2. For example, if the internal refrigerator temperature is higher than the set temperature by 5 degrees C. or greater, the controller 3 determines that the rotating speed is 3600 r.p.m. If the internal refrigerator temperature is higher than the set temperature by 2 degrees C. to 5 degrees C., the controller 3 determines that the rotating speed is 2400 r.p.m. If the internal refrigerator temperature is higher than the set temperature by 2 degrees C. or smaller or lower than the set temperature by 2 degrees C. or smaller, the controller 3 determines that the rotating speed is 1600 r.p.m. If the internal refrigerator temperature is lower than the set temperature by 2 degrees C. or greater, the controller 3 determines that the rotating speed is zero.

An AC/DC converter 4 is coupled to a utility power supply 5 and converts a utility AC voltage into a DC voltage. An input of an inverter circuit 6 is coupled to the AC/DC converter 4, and an output of the inverter circuit 6 is coupled to a DC motor 7.

The DC motor 7 is built into the compressor 8 (not shown) for cooling a refrigerator or the like.

The inverter circuit 6 includes six switching elements T1, T2, T3, T4, T5, and T6 which are connected by a three-phase bridge connection.

An inverter controller 10 is coupled to the controller 3 and causes the DC motor 7 to operate at a rotating speed determined by the controller 3.

The inverter controller 10 includes a position detection section 11, a commutation section 12, a rotating speed control section 13, a rotating speed calculation section 14, a set rotating speed detection section 15, a rotating speed comparison section 16, a composition section 17, and a drive section 18.

The position detection section 11 detects a position of a rotor based on a back EMF voltage of the DC motor 7, and outputs a position detection signal to the commutation section 12, the rotating speed control section 13 and the rotating speed calculation section 14.

The commutation section 12 outputs a driving commutation pulse to the composition section 17, based on the position detection signal from the position detection section 11.

The rotating speed calculation section 14 calculates the rotating speed of the DC motor 7 in such a manner that it counts the position detection signal from the position detection section 11 for a specified period or measures a pulse interval (pulse spacing) of the position detection signal, and outputs the rotating speed at which the DC motor 7 is operating, to the rotating speed comparison section 16.

The set rotating speed detection section 15 detects the set rotating speed sent from the controller 3 and outputs the set rotating speed to the rotating speed comparison section 16.

If the set rotating speed is zero, the rotating speed comparison section 16 outputs the rotating speed of “zero” to the rotating speed control section 13, and the DC motor 7 maintains its stopped (deactivated) state.

If the rotating speed is not zero, and is for example, 1600 r.p.m., the rotating speed comparison section 16 outputs the rotating speed of “1600 r.p.m.”, to the rotating speed control section 13. The rotating speed control section 13 starts the DC motor 7 if the DC motor 7 is in the stopped state.

The rotating speed comparison section 16 compares the rotating speed of the DC motor 7 from the rotating speed calculation section 14 to the set rotating speed from the set rotating speed detection section 15. If the rotating speed of the DC motor 7 is lower than the set rotating speed, the rotating speed comparison section 16 outputs a signal to increase a duty ratio to the rotating speed control section 13. In response to this signal, the rotating speed control section 13 increases the duty ratio and increases a voltage applied to the DC motor 7, thereby increasing the rotating speed of the DC motor 7.

On the other hand, if the rotating speed of the DC motor 7 is higher than the set rotating speed, the rotating speed comparison section 16 outputs a signal to decrease a duty ratio to the rotating speed control section 13. In response to this signal, the rotating speed control section 13 decreases the duty ratio and decreases a voltage applied to the DC motor 7, thereby decreasing the rotating speed of the DC motor 7.

The composition section 17 outputs logical product of the output of the commutation section 12 and the output of the rotating speed control section 13, to the drive section 18. The drive section 18 drives the inverter circuit 6.

Hereinafter, a description will be given of the operation for increasing and decreasing the rotating speed of the DC motor 7 built into the compressor 8, in conjunction with the control performed by the controller 3 configured as described above, with reference to FIG. 4.

Firstly, the controller 3 determines the rotating speed of the DC motor 7 based on the difference between the internal refrigerator temperature detected by the internal temperature detector 1 and the set temperature detected by the set temperature detector 2, and outputs the determined rotating speed to the inverter controller 10 as the set rotating speed.

In STEP 1, the inverter controller 10 receives the set rotating speed as an input, from the controller 3.

In STEP 2, the set rotational speed detection section 15 determines whether or not the input set rotating speed is zero. If it is determined that the input set rotating speed is zero, the DC motor 7 is stopped in STEP 3. On the other hand, if it is determined that the input set rotating speed is not zero, in STEP 4, the set rotational speed detection section 15 determines whether or not the DC motor 7 is in a stopped state. If it is determined that the DC motor 7 is in the stopped state, in STEPS, the set rotational speed detection section 15 performs control for starting the DC motor 7, to start the DC motor 7. After the control for starting the DC motor 7 finishes, in STEP 6, the rotating speed control section 14 calculates the rotating speed of the DC motor 7 based on the position detection signal from the position detection section 11. In STEP 7, the rotating speed comparison section 16 compares the set rotating speed set by the set rotating speed detection section 15 to the rotating speed of the DC motor 7 calculated by the rotating speed calculation section 14.

If it is determined that the calculated rotational speed is lower than the set rotational speed in STEP S8, in STEP 9, the rotational speed control section 13 increases the duty ratio to increase the rotating speed.

On the other hand, if it is determined that the calculated rotational speed is not lower than the set rotating speed in STEP S8, in STEP 10, it is determined whether or not the calculated rotational speed is higher than the set rotating speed. If it is determined that the calculated rotational speed is higher than the set rotating speed, in STEP 11, the rotating speed control section 13 decreases the duty ratio to decrease the rotating speed.

In the above described manner, the control process is performed so that the rotating speed reaches the set rotating speed, and the compressor 8 operates at a proper rotating speed according to an internal refrigerator load.

SUMMARY OF THE INVENTION

However, in the above described configuration, in the refrigerator which does not include the controller for determining the rotating speed of the operation of the compressor based on the difference between the internal refrigerator temperature and the set temperature, the rotating speed of the compressor cannot be determined.

As a solution to the above, the following control process may possibly be used. A thermostat which is turned ON/OFF based on the internal refrigerator temperature is used, an activation signal or a deactivation signal is input to the inverter controller, and the inverter controller starts the operation of the compressor at a low rotational speed in response to the activation signal, when the activation signal is input to the inverter controller, and increases the rotating speed of the operation of the compressor after a specified time passes. However, information relating to the thermostat is only ON/OFF temperature, and therefore a proper rotating speed of the operation of the compressor cannot be determined.

The present invention is directed to solving the above stated problem associated with the prior art, and an object of the present invention is to enable a compressor to operate at a proper rotating speed based on an internal load of a refrigerator which does not include a controller for determining the rotating speed of the operation of the compressor based on a difference between an internal refrigerator temperature and a set temperature.

To solve the problem associated with the prior art, according to one aspect of the present invention, a controller of a compressor is configured to operate the compressor at a constant rotating speed, detect a motor current corresponding to the constant rotating speed to detect a refrigerator load, and set a time at which the rotating speed of the compressor is increased based on a detection result of the refrigerator load. Therefore, the compressor can be operated at a proper rotating speed according to the refrigerator load.

The above stated controller of the compressor allows the compressor to operate at a proper rotating speed according to the refrigerator load. For example, when it is determined that the refrigerator load is great, the compressor is operated at a higher speed quickly, while when it is determined that the refrigerator load is smaller, the compressor is operated at a lower speed, which results in energy saving.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a circuit diagram of a controller of a compressor according to an embodiment of the present invention.

FIG. 2 is a flowchart showing the operation of the controller of the compressor according to the embodiment of the present invention.

FIG. 3 is a circuit diagram of a conventional controller of a compressor.

FIG. 4 is a flowchart showing the operation of the conventional controller of the compressor.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

According to a first present invention, there is provided a controller of a compressor which increases a rotating speed of the compressor at which the compressor operates, in response to an operation signal or a stop signal of the compressor, with a passage of a time; the controller being configured to operate the compressor at a constant rotating speed and detect a motor current corresponding the constant rotating speed to detect a load state of the compressor, and set a time at which the rotating speed of the compressor is increased, based on a result of detection of the load state of the compressor. In accordance with this configuration, the time at which the rotating speed of the compressor is increased can be set according to the load state of the compressor.

According to a second present invention, there is provided a controller of a compressor comprising: an operation/stop detection section for detecting an operation signal or a stop signal of the compressor; a rotating speed setting section for setting a rotating speed of the compressor at which the compressor operates, in response to the operation signal or the stop signal from the operation/stop detection section; an inverter circuit for rotating a motor built into the compressor; a position detection section which detects a position of a rotor of the motor and generates a position detection signal; a commutation section which determines an operation of the inverter circuit based on the position detection signal from the position detection section and outputs a commutation pulse; a rotating speed control section which adjusts a duty ratio which is a ratio of ON time with respect to a carrier cycle and controls a voltage to change the rotating speed of the compressor; a drive section for driving the inverter circuit based on an output of the commutation section and an output of the rotating speed control section; a rotating speed calculation section for calculating the rotating speed of the motor from the position detection signal from the position detection section; a rotating speed comparison section which compares the set rotating speed set by the rotating speed setting section to the rotating speed of the motor calculated by the rotating speed calculation section and outputs a signal to the rotating speed control section to enable the rotating speed of the motor to reach the set rotating speed; a motor current detection section for detecting a value of a motor current of the inverter circuit; and a timer which sets a time at which the rotating speed of the motor is increased based on the motor current value detected by the motor current detection section and outputs a signal to increase the rotating speed to the rotating speed setting section, when a time has reached the time set in the timer. In accordance with this configuration, the time at which the rotating speed is increased can be set for each rotating speed of the operation of the compressor. Therefore, the time at which the rotating speed of the compressor is increased can be set based on its load state.

According to a third present invention, in the first present invention or the second present invention, the controller may be configured to control a refrigerator and the time at which the rotating speed of the compressor is increased can be set according to the load state of the compressor. Therefore, in addition to the above advantages of the first present invention and the second present invention, the refrigerator can be operated properly.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Throughout the drawings, the same or corresponding components are designated by the same reference symbols, and will not be described in repetition. The present invention is in no way limited to the embodiment described below.

FIG. 1 is a circuit diagram of a controller of a compressor according to an embodiment of the present invention. FIG. 2 is a flowchart showing the operation of the controller of the compressor according to the embodiment of the present invention. Hereinafter, a method of determining the rotating speed of the operation of the compressor based on its load state and operating the compressor will be described with reference to FIGS. 1 and 2.

It is supposed that a compressor 108 shown in FIG. 1 is built into a refrigerator. Hereinafter, the embodiment will be described in conduction with how to control the refrigerator will be described.

A thermostat 101 detects an internal refrigerator temperature and is turned ON/OFF based on the detected internal refrigerator temperature.

An AC/DC converter 104 is connected to a utility power supply 105, and converts a utility AC voltage from the utility power supply 105 into a DC voltage. An input of an inverter circuit 106 is connected to the AC/DC converter 104 and an output of the inverter circuit 106 is connected to the DC motor 107.

The DC motor 107 is built into the compressor 108 for cooling the refrigerator or the like.

The inverter circuit 106 includes six switching elements T1, T2, T3, T4, T5, and T6, which are three-phase bridge connected.

The inverter controller 110 is connected to the thermostat 101. In a state in which the thermostat 101 is ON, the inverter controller 110 operates the DC motor 107, while in a state in which the thermostat 101 is OFF, the inverter controller 110 stops the DC motor 107.

The inverter controller 110 includes a position detection section 111, a commutation section 112, a rotating speed control section 113, a rotating speed calculation section 114, an operation/stop detection section 115, a rotating speed comparison section 116, a composition section 117, a drive section 118, a rotating speed setting section 120, and a timer 121.

The position detection section 111 detects a position of a rotor based on a back EMF voltage of the DC motor 107, and outputs a position detection signal to the commutation section 112, the rotating speed control section 113, and the rotating speed calculation section 114.

The commutation section 112 outputs a driving commutation pulse to the composition section 117 based on the position detection signal from the position detection section 111.

The rotating speed calculation section 114 calculates the rotating speed of the DC motor 107 in such a manner that it counts the position detection signal from the position detection section 111 for a specified period of time, or measures a pulse interval of the position detection signal. The rotating speed calculation section 114 outputs the calculated rotating speed of the DC motor 107 to the rotating speed comparison section 116.

The operation/stop detection section 115 detects an “Operation” signal or a “Stop” signal sent from the thermostat 101, and outputs the detected signal to a rotating speed setting section 120.

The rotating speed setting section 120 outputs a signal indicating the rotating speed to the rotating speed comparison section 116. At this time, when the signal indicating the state of the thermostat 101 is “Stop” signal, the rotating speed setting section 120 outputs the rotating speed “zero” to the rotating speed comparison section 116. On the other hand, when the signal is “Operation” signal, the rotating speed setting section 120 outputs a signal indicating a minimum rotating speed, for example, 1600 r.p.m.

The rotating speed comparison section 116 outputs to the rotating speed control section 113, a signal for causing the DC motor 107 to rotate at 1600 r.p.m. In response to this signal, the rotating speed control section 113 causes the DC motor 107 to operate at 1600 r.p.m.

The rotating speed comparison section 116 compares the rotating speed of the DC motor 107 to the set rotating speed from the rotating speed setting section 120. When the rotating speed of the DC motor 107 is lower than the set rotating speed, the rotating speed comparison section 116 outputs a signal to increase a duty ratio to the rotating speed control section 113. In response to this signal, the rotating speed control section 113 increases the duty ratio and increases a voltage applied to the DC motor 107, thereby increasing the rotating speed of the DC motor 107. On the other hand, when the rotating speed of the DC motor 107 is higher than the set rotating speed, the rotating speed comparison section 116 outputs a signal to decrease the duty ratio to the rotating speed control section 113. In response to this signal, the rotating speed control section 113 decreases the duty ratio and decreases the voltage applied to the DC motor 107, thereby decreasing the rotating speed of the DC motor 107.

The composition section 117 outputs logical product of the output of the commutation section 112 and the output of the rotating speed control section 113 to the drive section 118. The drive section 118 drives the inverter circuit 106.

The timer 121 receives a motor current corresponding to rotation of 1600 r.p.m., from a motor current detector 122, for a specified period of time. When the motor current is greater, the timer 121 determines that the load is greater, and sets a time passing before increasing the rotating speed to a shorter time. On the other hand, when the motor current is smaller, the timer 121 determines that the load is smaller, and sets the time before increasing the rotating speed to a longer time.

This is because, it can be determined that, when the DC motor 107 is operated at a constant rotating speed, the motor current is greater as the load is greater, whereas the motor current is smaller as the load is smaller, and thus, it can be determined whether the load is greater or smaller based on the magnitude of the motor current.

Generally, in a case where the temperature of food stored in the interior of the refrigerator is high or an outside air temperature is high, the load of the compressor 108 is greater. In this case, it is necessary to quickly cool the refrigerator by rotating the compressor 108 at a higher rotating speed. On the other hand, in another case where the food stored in the interior of the refrigerator is adequately cooled, or an outside air temperature is low, the load of the compressor 108 is smaller. In this case, it is not necessary to rotate the compressor 108 at a higher rotating speed. Therefore, the compressor 108 is operated at a lower rotating speed, and thus, power saving is achieved.

When a time has reached the set time, the timer 121 outputs a signal to increase the rotating speed, to the rotating speed setting section 120. In response to this signal, the rotating speed setting section 120 increases the rotating speed.

Next, the operation in which the rotating speed of the operation of the compressor 108 is determined based on its load state and the DC motor 107 is operated at the determined rotating speed, will be described with reference to FIG. 2.

Initially, in STEP 101, the inverter controller 110 receives the signal from the thermostat 101 and determines whether or not the signal is the “Operation” signal or “Stop” signal.

If it is determined that the signal is the “Stop” signal, in STEP 114, the inverter controller 110 clears an accumulated time in the timer 121. Then, in STEP 115, the inverter controller 110 stops the DC motor 107.

On the other hand, if it is determined that the signal is the “Operation” signal, in STEP 5102, the inverter controller 110 causes the DC motor 107 to rotate at 1600 r.p.m.

Then, in STEP 103, after a passage of a specified period of time after start of the rotation of the DC motor 107, a motor current of the DC motor 107 rotating at 1600 r.p.m. is detected.

Then, in STEP 104, the inverter controller 110 determines whether or not the motor current is not greater than, for example, 0.5 A. If it is determined that the motor current is not greater than 0.5 A, in STEP 105, the set value of the timer 121 is set to 30 minutes. On the other hand, if it is determined that the motor current is greater than 0.5 A, in STEP 106, the inverter controller 110 determines whether or not the motor current is not greater than, for example, 0.6 A. If it is determined that the motor current is not greater than 0.6 A, in STEP 107, the set value of the timer 121 is set to 20 minutes. If it is determined that the motor current is greater than 0.6 A, in STEP 108, the set value of the timer 121 is set to 10 minutes. After setting the time in STEP 105, in STEP 106, and in STEP 107, the timer 121 starts measuring a time.

Then, in STEP 109, the inverter controller 110 receives the signal from the thermostat 101 as an input, and determines whether this signal is the “Operation” signal or “Stop” signal. If it is determined that the signal is the “Stop” signal, in STEP 114, the inverter controller 110 clears an accumulated time in the timer 121. Then, in STEP 115, the inverter controller 110 stops the DC motor 107.

On the other hand, if it is determined that the signal is the “Operation” signal, in STEP 110, the inverter controller 110 determines whether or not a time has reached the time set in the timer 121. If it is determined that a time does not reach the time set in the timer 121 yet, in STEP 113, the timer 121 accumulates (counts up) the time. On the other hand, if it is determined that the time has reached the time set in the timer 121, in STEP 5111, the timer 121 outputs a signal to increase the rotating speed up to, for example, 2400 r.p.m., to the rotating speed setting section 120, and the rotating speed setting section 120 outputs a signal for causing the DC motor 7 to rotate at 2400 r.p.m., to the rotating speed comparison section 116. In response to this signal, the rotating speed comparison section 116 outputs a signal to increase the duty ratio to the rotating speed control section 113.

Then, in STEP 112, the timer 121 is cleared and the process returns to STEP 109.

Thus, whether the load is greater or smaller is determined, based on the detected motor current corresponding to the constant rotating speed. When the load is greater, the rotating speed of the DC motor 107 is increased quickly, whereas when the load is smaller, the rotating speed of the DC motor 107 is not increased but operated at a lower rotating speed. This enables the compressor to operate according to its load state.

Although the case where the rotating speed of the operation of the DC motor 107 is increased from the minimum rotating speed of 1600 r.p.m. has been described above, further, the motor current of the DC motor 107 rotating at 2400 r.p.m. increased from 1600 r.p.m may be detected, and a time at which the rotating speed is increased from 2400 r.p.m. up to 3600 r.p.m. may be changed according to the load.

Under the state in which the load of the DC motor 107 is constant, the motor current is unchanged even when the rotating speed changes. Therefore, a desired rotating speed can be selected in the operation at the constant rotating speed.

As should be appreciated from the above, the controller of the compressor of the present invention is capable of controlling the rotating seed of the compressor based on the load state without a need for the controller of the refrigerator. Therefore, the present invention is useful in control for an inverter driving device of a compressor constituting a refrigeration device, or in control for refrigerators for commercial purposes or household use.

As this invention may be embodied in several forms without departing from the spirit of essential characteristics thereof, the present embodiments are therefore illustrative and not restrictive, since the scope of the invention is defined by the appended claims rather than by the description preceding them, and all changes that fall within metes and bounds of the claims, or equivalence of such metes and bounds thereof are therefore intended to be embraced by the claims. 

1. A controller of a compressor which increases a rotating speed of the compressor at which the compressor operates, in response to an operation signal or a stop signal of the compressor, with a passage of a time; the controller being configured to operate the compressor at a constant rotating speed and detect a motor current corresponding the constant rotating speed to detect a load state of the compressor, and set a time at which the rotating speed of the compressor is increased, based on a result of detection of the load state of the compressor.
 2. A controller of a compressor comprising: an operation/stop detection section for detecting an operation signal or a stop signal of the compressor; a rotating speed setting section for setting a rotating speed of the compressor at which the compressor operates, in response to the operation signal or the stop signal from the operation/stop detection section; an inverter circuit for rotating a motor built into the compressor; a position detection section which detects a position of a rotor of the motor and generates a position detection signal; a commutation section which determines an operation of the inverter circuit based on the position detection signal from the position detection section and outputs a commutation pulse; a rotating speed control section which adjusts a duty ratio which is a ratio of ON time with respect to a carrier cycle and controls a voltage to change the rotating speed of the compressor; a drive section for driving the inverter circuit based on an output of the commutation section and an output of the rotating speed control section; a rotating speed calculation section for calculating the rotating speed of the motor from the position detection signal from the position detection section; a rotating speed comparison section which compares the set rotating speed set by the rotating speed setting section to the rotating speed of the motor calculated by the rotating speed calculation section and outputs a signal to the rotating speed control section to enable the rotating speed of the motor to reach the set rotating speed; a motor current detection section for detecting a value of a motor current of the inverter circuit; and a timer which sets a time at which the rotating speed of the motor is increased based on the motor current value detected by the motor current detection section and outputs a signal to increase the rotating speed to the rotating speed setting section, when a time has reached the time set in the timer.
 3. controller of the compressor according claim 1, configured to control a refrigerator.
 4. controller of the compressor according claim 2, configured to control a refrigerator. 